Correct me if I'm wrong, but to a great extent, the spread and total for NBA basketball is based on each team's scoring capability, right? So if that's the case, why is it that during the first week of the NBA, lines are already sharp, falling within a narrow range and in many cases just a few points off the actual scores?

There are very few surprises; faves win and dogs lose SU (covering is another matter). This is true even for the first 3 days of the 2012-13, where teams are just playing their first games of the season.

So what are the linesmakers basing their projected totals and spreads on that part of the season?